A couple of years ago, I got liquid in my MacBook Pro 5,2 (Unibody 17" Early 2009). After that, the display never worked. Apple Stores and Authorized Repair places insist on me paying over $1000 for a full logic board replacement before they'll do anything else to it, so I've been using it as a desktop machine with an external display since then.

Sometimes I leave the computer's display propped halfway open to help with heat. It's been that way for days. Tonight I briefly had a USB hub go funky, with lights blinking that shouldn't have been blinking, so I restarted the computer.

When it restarted, the years-dead display worked. But it didn't work perfectly; solid-white and solid-black areas flickered shades of yellow, green, and blue incessantly. But those flickering corrupted areas moved perfectly with app windows as I dragged them around, so I think it was some kind of corruption of the graphics data and not physically broken display pixels that I was seeing.

I was elated, and started trying to fix the display. First, I rebooted. Didn't help; after the reboot it looked just as it did before. So, step 2, I zapped the PRAM.

On that reboot, the display stayed dark, just as it has for years. I zapped the SMC after that, and the display is still dark. Clicking "Detect Displays" in System Preferences doesn't help.

I'm furious that this thing got my hopes up and immediately squashed them. Is there anything, no matter how complicated or technical, that I can do to make this thing acknowledge that display? I am 100% comfortable with the command line or anything even more arcane that I need to try.

All right, I guess I'm going to go down this rabbit hole. I just ordered a Tri-wing screwdriver to remove the battery with. I'll report back later this week with the results of my tinkering.
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75th TromboneMay 18 '13 at 23:19

Well, I opened up the Mac, and sure enough, there was gunk on the display data cable. I removed it, cleaned all around it, plugged it back in… …and still nothing. When I saw it I was sure cleaning it was going to work, but nothing doing. My next step is to take it to an independent Mac repair place for an $80 diagnosis, and if they find what's wrong I will make them tell me precisely what it is.
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75th TromboneMay 25 '13 at 21:54

Well, the story has a happy ending! The display didn't work immediately after I put it together, but after I used it for a bit, plugged it into an external monitor, etc., it started working without the flickering or corruption. So it's good as new again! Thanks so much.
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75th TromboneJun 26 '13 at 20:56

You are welcome. Sometimes the good old ways work. PS, that it did not work immediately indicates oxidized contact of the plugs :)
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Buscar웃Jun 26 '13 at 21:55

Years ago, an independent Mac repair guy opened up the case of a Powerbook on which I'd spilled a little coffee, poked very gently around with a q-tip, probably with alcohol on it, but maybe only water, cleaning up all the little dried granules he could see.

Note that I am not recommending you do this, just passing along a story.

He also knew what wire went where--fixed several of my machines over the years. Are those kind of guys still around? Find one.

There used to be information on the web about bringing a "dead" Powerbook back to life. Google is, in this case, your friend.

One thing with weird hardware errors (assuming it maybe one), is that they sometimes come and go randomly. This can be pretty mean, because this randomness (a) usually coincides with something you do (b), because you're doing all kinds of things and it happens just during one of those. Which makes you think (b) caused (a) (in your case PRAM reset caused it to break again).

I'm not saying it's clearly a hardware error (it could be a broken or damaged flat wire or a thermal thing), just don't necessarily jump to conclusions about what caused what.